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Is springtime also pothole season?

Is springtime also pothole season?

Yes. Early spring can be considered pothole season. Many roadways are constructed in layers. The top layer is water resistant and curved to drain water off the road and onto the shoulder. Eventually the road surface develops cracks due to the stresses caused by traffic and because of the heating and cooling of the surface. During the day, the sun warms the roadway causing it to expand a small amount while nighttime cooling causes the road to contract.

Once the cracks form, water can seep below the surface into the underlying materials. During the cold nights the water freezes and expands. During a clear sky day, the sun warms the road which melts the underlying ice, and the water flows to a different section of the roadway, leaving behind a small empty space. Further stresses on the roadway widen existing cracks, allowing more water to seep in and freeze during the night. This enlarges the crevice. Eventually the space crumples under the stress and a pothole forms.

A winter with lots of snow provides a moisture source for potholes. We see many potholes develop in the spring as that is when we get night time temperatures below freezing and daytime temperatures above freezing due to the longer daylight hours. This temperature cycle results in several freeze-thaw cycles that cause potholes.

Repairing potholes is a challenge as one has to not only fill the hole but also seal it to keep water from getting into any cracks.

Steven A. Ackerman and Jonathan Martin are professors in the Department of Atmospheric and Oceanic Sciences at UW-Madison, are guests on the Larry Meiller‘s WHA-AM radio show the last Monday of each month at 11:45 a.m.